This invention has a broad range of applications, however, for convenience of explanation it will be described in the context of what is known as acoustic micro imaging (“AMI”) in which an acoustic microscope is employed to detect minute features within or on the surface of an examined sample. AMI is commonly employed in material and process analysis, failure analysis, non-destructive testing, and production quality control and inspection, for example.
AMI is based upon the fact that acoustic waves traveling through a sample of homogenous material will be altered when the waves encounter an anomaly of some type. If the anomaly has a different acoustic impedance than the sample material, the waves will be reflected, refracted, deflected or scattered. If the anomaly has a different acoustic absorption characteristic than the sample material, a differential absorption of the acoustic wave will occur. Under certain conditions the wave may be converted from one form to another, as compressional wave to shear wave or surface wave. AMI takes advantage of these alterations of an interrogating acoustic wave by an anomaly to produce visual displays of the interior of an examined sample.
It is common in AMI inspection and visualization applications for the internal region of interest in an inspected sample to be small in comparison with the dimensions of the sample. In such applications it is often difficult for the user to physically correlate in space the micro location of the inspected region of interest with the macro space occupied by the sample.
An example of this is in the AMI inspection of printed circuit (“PC”) boards (“PCBs”). A PCB may, for example, be twelve or more inches long and mount dozens of components. Typically only a few of the components are inspected—e.g., integrated circuits (“ICs”).
The user would typically have access to visualizations of a variety of AMI “slices” taken at various depths in selected inspected components on the PCB. These visualizations often show impedance features of interest within the examined samples, such as die or die lead disbonds, cracks, epoxy underfill voids, and so forth. This is extremely valuable information, but it is uncorrelated with the PCB. The user is plagued by questions such as: Which examined components exhibit which of the visual anomalies? What is the correct spatial orientation of the acoustic visualization relative to the PCB? How does the scale of the visualized sample relate to the scale of the IC or other parts on the PCB?
A need thus exists for a method which correlates AMI micro imagery with the macro space of the inspected sample or collection of samples, with correct spatial orientation and scaling. It is an object of the present invention to meet this need.
In the design and manufacture of PCB assemblies, it is of interest to know whether the general layout of components on the board is optimum. Designers would like to know, e.g., whether the locations of the components producing the most heat are such that those components will affect the performance or reliability of other components. Under current practice, AMI inspections are performed on various PCB parts scattered across the board, but no information is available that might suggest a relationship between detected defects or anomalies on various parts. There is no simple way of predicting whether the placement of a microprocessor or power amplifier or other heat-producing element, for example, is deleteriously affecting the life or performance of adjacent components.
It is another object of the present invention to meet the described need by providing a method which makes possible the correlation of macro visualizations (such as a full PCB) with micro AMI visualizations, and which in so doing facilitates an improved understanding of interactive effects between spatially separated parts.
In current AMI practice a number of images, representing slices in X-Y planes perpendicular the Z direction of the acoustic probe, will be created at Z-various depths in an examined sample (which can include a surface slice). These X-Y slices may be closely adjacent in the Z dimension, but frequently are sufficiently spaced as to visualize different anomalies. It is not uncommon to visualize in transparent mode a chosen group of adjacent ones of these slices. Upon occasion it would be of great interest to better understand how the anomalies visualized in selected internal slices of arbitrary location correlate with surface features, or how slices (internal or surface) in different sized fields of view correlate.
It is another object of the present invention to satisfy the described need for spatial correlation between selected internal slices and surface features of the examined part, or between selected internal slices in different sized fields of view.
In certain implementations of the present invention, images formed by disparate methodologies are overlaid in a common rendering. It is still another object to rectify all correlated images to assure accurate orthography and scaling of overlaid images.
In production quality and process control, laboratory analysis, failure analysis, and other applications, as much information as possible is desired to be obtained about the parts or samples of interest. It is of obvious interest to correlate the information collected in order that additional information can be gleaned from the correlations.
It is yet another object of the present invention to provide a method for correlating information generated using disparate energy forms, including optical, infrared, acoustical, and other, and different capture techniques, including AMI and other acoustic imaging, photography, thermography, electron beam microscopy, X-ray and other.
It is a further object to provide display and visualization methods to enhance the information developed from overlays of images developed from like and/or disparate energy forms and techniques.